Adjustable condenser



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` INVENTOR. Zea/M176. ,5a/Masi Patented Dec. 2l, 1.926.

UNITED STATES LEONARD G. BURKWEST, OF CHICAGO, ILLINOIS.

ADJUSTABLE CONDENSER.

Application filed August 14,' 1924.

This invention relates to improvements in adjustable electric condensers, and while the invention may be applied in any circuit where an adjustable condenser is indicated, it is particularly applicable, by reason of its compactness and of the minute and uniform adjustments of the condenser elements, to the circuits of radio receiving sets.

The principal object of the invention is to produce a novel adjustable condenser in which the variation of capacity can be et fected by flexing the condenser plates one toward the other, and characterized further in the fact that when the condenser is adjusted to its lowest capacity the movable plate is farthest removed from the other plate and is insulated by an adjustable air gap and a fixed dielectric, so that when the end of the movable plate is brought towards and against the dielectric the increasing capacity of the condenser is effected, first, by causing the movable plate to advance towards the dielectric and the other plate at an angle producing a wedge-shaped space, which space assumed a closed wedgeshape when the movable plate contacts with the dielectric, and, second by causing the flexible plate, during continued advancement of the movable plate towards the other plate, gradually to decrease the length or depth of the V-shaped space separating the movable and other plate with the dielectric interposed therebetween until said angle between the movable and the dielectric vanishes, or substantially s'o, at the point of largest capacity of the condenser where the plates rare substantially parallel with each other. Conveniently, and as herein shown, the total movement to vary the capacity of the condenser is effected by the movement of one flexible plate towards the dielectric [hat lies on another fixed plate, but this relative movement of the plates may within the spirit of the claims hereto attached be manifested by movement of both plates towards each other by suitable means which will bring the plates into parallelism, with one plate flat on the dielectric when rthe condenser is. adjusted to its'largest capacity. y

The utility of this arrangement of the plates and dielectric is manifested in that the movable plate in the lowest capacity of the con-denser is spaced at the greatest distance over its entire length, within the Serial No. 732,042.

limits of the condenser, from the other plate by a body of air and the fixed dielectric, and the fact that this body of air, upon approach of the end of the movable plate towards the dielectric, is gradually lessened in its characteristic of a dielectric until the other end of the movable flexible plate is brought into rContact with the dielectric, and thereafter the V-wedge shaped space formed between coacting movable condenser plate and dielectric is gradually decreased and vanishes when the movable plate approaches parallelism with the dielectric of the other plate, thereby imparting to the condenser r a uniform increased capacity when moving in one direction, and a decreased capacity when moving in the opposite direction.

A further and important object of the invention is to produce a condenser of this general type wherein that one of the condenser plates which is relatively movable towards the other condenser plate and dielectric is pointed or sharpened at its free end or the first point of Contact of the plate with the dielectric.

It is desirable that the change in capacity be practically uniform throughout the range of adjustment of a condenser of this kind. The purpose of making the movable plate pointed at its free end is to avoid an abrupt change in capacity at the moment that. the point comes in contact with the dielectric, and therefore the change in capacity of the condenser takes place at a substantially uniform rate throughout the entire range of adjust-ment of the condenser.

As before stated, one of they plates may be fixed, and the other movable towards it, or both plates may be movable towards each other, and either of the plates may carry the dielectric within the scope of the appended claims.

Other objects of the invention are to otherwise simplify and improve adjustable condensers, and the invention comprises the elements and combination of elements shown in the drawings and described in the specification, and is pointed out in the appended claims.

Referring now to one embodiment of the invention illustrated in the drawing:

Figure l is a plan view of a variable condenser embodying my invention.

Figure 2 is a vertical section on the line A- Of Figure l.

Figure 3 is an end view of the condenser.

a strip ot flexible electric conducting rial. A1' the base ot its point 3, it is erably made of the same width as the plate. The .said movable plate is su anchored in the casing and extends from 'icr connection with a conductor 'i circuit in which the condenser is included. The fixed plate 2 lilewile extends m its support or casing for connection in ns circuit.

Then the condenser is adjusted tor its smallest capacity, it assumes the position indicated in dotted lines in Figure 2,r being in line with its anchor end.

Any suitable means may be employed in the en'ibodiment shown for moving the f end 3 of the plate towards the dielectric 6 which is superposed on the plate 2. rl`he active moving means herein shown comprises a screw 5 which may be threaded through a lixed abutment, as a casingwall, in which the condenser elements are enclosed. and gages at its inner end with that. part ol the condenser plate 3 near the base of its pointed end 3. When the free end of the Conductor 3 occupies the position indicated in dotted lines in Figure 2, it is separated from the plate 2 by the dielectric and air gap between the dielectric and the tree end of said movable plate. Pressure applied to the movable plate tlirough the action of the screw 5, or

other e uiva-lent ad'ustine means-has theA eflect to gradually decrease the angle of the `free end of the movable plate relatively to the lixed plate and thus decrease capacity between. the free pointed end of thc'movalille plate and theV plate 2.

Then the free end of the plate 3 strilaes the dielectric 6, said free end is caused lo be flexed in the manner shown in, full lines in Figure 2, the fiexation occurring in the theretoitore angle portion of the -ree end o the movable member. As pressure is increased on said movable plate, the latter plate will flex beginning at its point, and this liexation will continue as the pressure is continued until the wedge-shaped body of airis eliminated between the iiexing movable plate and the dielectric, whereupon said alates are parallel with each other and with the dielectric between them, thus producing the greatest amount 0In capacity for which the condenser'is adapted.

Many forms of casings to support and enclose the. condenser elements may be provided. l have herein shown a simple two part casing made of insulating material ccnsisting of separately ina-de wall i and bottom wall Il. Each wall l and d is formed at one end with right angle extensions T, 8 which, respectively, bear against the r' tively opposite ends the walls l and and the parts ot the casing bus formed are joined together by rivets '9. rlhe lo wall l ot the casing is of less width than the total width of the lower side of the casing, as shown in full lines in Figure Sand dotted lines in vFigure l, and the condenser plates 2 and 3 are clamped between their respective right angle portions i', S and the inner aces'of the straight portions of said walls, as best shown in Figure 2. rlhe lower wall member e is spaced from the right angle extension 7 of the upper wall, and the right angle extension 8 of the lower wall is spaced from the inner face ot the upper wall a distance to clamp the condenser plates between the casing members. he extension 8 constitutes in effect a fulcrum by which the movable condenser element is anchored whereby the first point of flexation of said condenser plate 3 is a distance inwardly from said extension 8, as indicated in Figure 2.

The casing for supporting and enclosing the dielectric parts has been described as indicating a. suitable casing for'this purpose, but it is intended that the description of a practical casing is intended to be illustrative and not limitative.

The condenser above described has been 'found in practice to be exceedingly Yuniform in its variations of capacity, and is well adapted to current of low value such as are used in radio receiving sets. lllhile the condenser has been constructed for low current, it will be understood that the principles thereotl may be advantageously employed in .circuits carrying higher value current.

l claim as my invention l. An adjustable electric condenser com.- prising a plurality of opposing plates and an interposed dielectric, characterized in that one or" the plates is flexible, anchored Yand free-ended, and that pressure .is applied to the flexible' plate between its free end and its anchored part to bring its free end into proximity to the other plate and to the dielectric y and then cause it'progressively to be flexed y into proximity to the other plate and'to the dielectric from its 'free end toward the anchored part. I K Y 2. An adjustable condenser Comprising a plurality of plates spaced apart-from cach other, one of the plates being flexible, anchored and free-ended, and Vmeans for manipulating the flexible plate so as to cause its free end to be brought into proximity Ytothe other plate and then to be bent progres :ill

sively from the free end toward the anchored part to lay it in proximity to the other plate.

An adjustable electric condenser, com4 prising a plurality of opposing plates and an interposed dielectric, characterized in that one plate is anchored and free ended and that pressure is applied thereto between its free end and anchored part to vary its en gagement with and angularity to the dielec- 'l tric, and thereby vary the capacity of the condenser, the free end of one plate being sharply pointed and tapering gradually back to its greatest width, and means whereby pressure first causes point Contact between '5 said pointed plate and said dielectric and thus producing V angle between it and the dielectric, and whereby continued pressure causes said angle to disappear and bring said plates to parallelism.

4. An adjustable condenser comprising two parallel plates spaced a considerable distance apart from each other, one end of one of the plates being fixed with respect to the corresponding end of the opposite plate and its other end being free, a dielectric interposed between said plates, and means for flexing the latter plate free end first into proximity to the other plate and then progressively flattening it so as to lay the greater portion thereof in proximity to the other plate.

5. An adjustable condenser comprising a plurality of plates spaced apart from each other, one of the plates being flexible, one end of the flexible plate being spaced in fixed relation to the other plate and the other end ofthe flexible plate being free, and means for manipulating the flexible plate so as to cause its free end to be brought into proximity to the other plate and then to cause a considerable length of the flexible plate to be laid flat in proximity to the other plate.

In testimony whereof I claim the foregoing as my invention, I hereunto append my signature this 13th day of August, 1924.

LEONARD G. BURKWEST. 

